1. Field of the Invention
The present invention relates to a screw fastening machine that performs a screw fastening operation by a tool bit which is rotationally driven by a motor, and more particularly to a screw fastening machine that has a function of regulating a screw fastening depth.
2. Description of the Related Art
As a representative example of a screw fastening machine, Japanese laid-open patent publication No. 2000-246657 discloses an electric screwdriver designed and configured such that a screw fastening operation is completed when a screw is driven to a predetermined depth. In the known screwdriver, a screw fastening depth regulating member for regulating the screw fastening depth is provided in the tip end region of a machine body. When a screw is driven into a workpiece to a predetermined depth in a screw fastening operation, the screw fastening depth regulating member contacts the surface of the workpiece. Therefore, the user is prevented from further moving the machine body in the screw fastening direction. Further, the force of rotationally driving the driver bit is cut off via a clutch member, so that the screw fastening operation by the driver bit is completed.
The screw fastening depth regulating member provided in the tip end region of the machine body may interfere with a screw fastening operation, for example, when the screw fastening operation is performed in a tight place. In such a case, the screw fastening depth regulating member may be removed from the machine body for the screw fastening operation. In this case, the removed screw fastening depth regulating member must be kept by the user or kept in an appropriate place within the work site. However, such has a possibility of losing the screw fastening depth regulating member. Therefore, further improvement is required in this respect.